/**
 * 项目名称：quickstart-datasource 
 * 文件名：JDBCExample.java
 * 版本信息：
 * 日期：2018年10月16日
 * Copyright yangzl Corporation 2018
 * 版权所有 *
 */
package org.quickstart.database.datasource.jdbc;

/**
 * JDBCExample 
 *  
 * @author：youngzil@163.com
 * @2018年10月16日 上午10:39:19 
 * @since 1.0
 */
import java.sql.*;

public class JDBCExample {
    // JDBC driver name and database URL
    static final String JDBC_DRIVER = "com.mysql.jdbc.Driver";
    static final String DB_URL = "jdbc:mysql://localhost/EMP";

    // Database credentials
    static final String USER = "username";
    static final String PASS = "password";

 public static void main(String[] args) {
   Connection conn = null;
   try{
      //STEP 2: Register JDBC driver
      Class.forName("com.mysql.jdbc.Driver");

      //STEP 3: Open a connection
      System.out.println("Connecting to database...");
      conn = DriverManager.getConnection(DB_URL,USER,PASS);

      //STEP 4: Execute a query to create statment with
      // required arguments for RS example.
      System.out.println("Creating statement...");
      Statement stmt = conn.createStatement(
                           ResultSet.TYPE_SCROLL_INSENSITIVE,
                           ResultSet.CONCUR_UPDATABLE);
     //STEP 5: Execute a query
      String sql = "SELECT id, first, last, age FROM Employees";
      ResultSet rs = stmt.executeQuery(sql);

      System.out.println("List result set for reference....");
      printRs(rs);

      //STEP 6: Loop through result set and add 5 in age
      //Move to BFR postion so while-loop works properly
      rs.beforeFirst();
      //STEP 7: Extract data from result set
      while(rs.next()){
         //Retrieve by column name
         int newAge = rs.getInt("age") + 5;
         rs.updateDouble( "age", newAge );
         rs.updateRow();
      }
      System.out.println("List result set showing new ages...");
      printRs(rs);
      // Insert a record into the table.
      //Move to insert row and add column data with updateXXX()
      System.out.println("Inserting a new record...");
      rs.moveToInsertRow();
      rs.updateInt("id",104);
      rs.updateString("first","John");
      rs.updateString("last","Paul");
      rs.updateInt("age",40);
      //Commit row
      rs.insertRow();

      System.out.println("List result set showing new set...");
      printRs(rs);

      // Delete second record from the table.
      // Set position to second record first
      rs.absolute( 2 );
      System.out.println("List the record before deleting...");
      //Retrieve by column name
      int id  = rs.getInt("id");
      int age = rs.getInt("age");
      String first = rs.getString("first");
      String last = rs.getString("last");

      //Display values
      System.out.print("ID: " + id);
      System.out.print(", Age: " + age);
      System.out.print(", First: " + first);
      System.out.println(", Last: " + last);

     //Delete row
      rs.deleteRow();
      System.out.println("List result set after deleting one records...");
      printRs(rs);

      //STEP 8: Clean-up environment
      rs.close();
      stmt.close();
      conn.close();
   }catch(SQLException se){
      //Handle errors for JDBC
      se.printStackTrace();
   }catch(Exception e){
      //Handle errors for Class.forName
      e.printStackTrace();
   }finally{
      //finally block used to close resources
      try{
         if(conn!=null)
            conn.close();
      }catch(SQLException se){
         se.printStackTrace();
      }//end finally try
   }//end try
   System.out.println("Goodbye!");
}// end main

    public static void printRs(ResultSet rs) throws SQLException {
        // Ensure we start with first row
        rs.beforeFirst();
        while (rs.next()) {
            // Retrieve by column name
            int id = rs.getInt("id");
            int age = rs.getInt("age");
            String first = rs.getString("first");
            String last = rs.getString("last");

            // Display values
            System.out.print("ID: " + id);
            System.out.print(", Age: " + age);
            System.out.print(", First: " + first);
            System.out.println(", Last: " + last);
        }
        System.out.println();
    }// end printRs()
}// end JDBCExample
